In Vivo Tagging and Characterization of S‐Glutathionylated Proteins by a Chemoenzymatic Method

Glutathionylspermidine synthetase (GspS) was introduced into human cells to label endogenous glutathione (GSH) with biotinyl spermine (biotin-spm) for the identification of S-thiolated proteins. The proteins carrying Gspm-biotin can be detected by immunoblotting (A in figure). Enrichment by using the biotin tag enabled subsequent mass-spectrometry-based proteomic analysis (B) for site-specific identification of glutathionylated sites.